"The Portrait of a Lady", as they've called it with a nod to Sargent's friend and fellow ex-patriot American Henry James, is a biographical exhibition twice over. It presents, in miniature, the story of Sargent's career and of the subject whose celebrated beauty catapulted them both into the public eye when her portrait was first exhibited at the Royal Academy in 1893.
Sargent's name was already known by then. His smouldering, snooty portrait of Madame Gautrea had shocked Paris society nearly 10 years earlier, and his masterly marriage of Impressionism and Pre-Raphaelitism, Carnation Lily Lily Rose, had been bought for the British nation as early as 1887. It was, however, Lady Agnew that established his credentials as the painter of Edwardian society and brought queues of London's most fashionable to his studio door.
It is a remarkable picture: faultlessly beautiful and perfectly painted. She sits, slightly slumped in a bergere, one arm trailing down its side. Her white gown and purple sash, the Chinese hanging behind her head and the loosely brushed flowers that decorate the chair are all painted with matchless virtuosity. Like most of Sargent's best work, the Agnew portrait is most exciting at its edges, the freer and bolder the better, but, unusually for him, this picture has an added quality that marks it apart. There is, in her look, a hint of psychological tension, as if she may actually be thinking about something other than being painted. It may have helped that she was ill at the time; a little distracted perhaps, but the effect is a far more serious picture than those that surround it.
There are 23 other works by Sargent in the exhibition and a number by his contemporaries, but there is nothing in any of them that comes close to the brilliance of Lady Agnew. Remarkable as it is, I'm not sure that it justifies an exhibition to itself: for all of the gilded glamour that fills these canvases, the experience of the show doesn't add up to very much. The paintings, like some of the people they depict, seem too much like the triumph of style over content.
Late in his career, having turned from portraiture to landscape, fed up with what he perceived as the vacuity of his former profession, Sargent said that "a portrait is a picture in which there is something wrong with the mouth". Step next door to the Raeburn exhibition at the RSA and you'll realise that in other hands, and other times, the art of portraiture offers other, more satisfying alternatives.
`The Portrait of a Lady: Sargent and Lady Agnew' to 19 October (0131- 624 6200)